Q: Dear Tom and Ray:

Would it be crazy to put a rebuilt engine in a 12-year-old car? I use my old Mazda wagon as a dogmobile for my dog-walking business. I've been looking at new cars, but I don't think I could stand it if the dogs scratched up the inside of a new car like they've done to this old one. Will a rebuilt engine give my Mazda a new lease on life?

--Sally

A: RAY: Absolutely. You're the perfect candidate for a rebuilt engine, Sally. In fact, the American Association of Engine Rebuilders will probably want you to star in their next TV commercial.

TOM: Here's your situation, Sally: You have a car that--aside from a worn-out engine--serves you perfectly well. So why spend a ton of money on a new, or newer, car that you don't even really want? Just throw an engine in it.

RAY: The one thing that you absolutely have to do, though, is have the rest of the old Mazda thoroughly checked out before you put the engine in. Have a mechanic you trust go over the beast from headlight to tailpipe--as if you were going to buy it as a used car. Find out everything that's wrong with it and factor that into your calculations.

TOM: So, for instance, if it needs new shocks, that's no big deal. You put in an engine and shocks and you're happily toting the doggies around again.

RAY: But if you find out that you also need a new transmission and your frame is rusted, then you might want to reconsider.

TOM: I've got it. If it's not worth putting an engine in it, she could just rig up a harness and let the dogs pull her. How many Pekingese does it take to pull a Mazda?

RAY: I'll have to look it up. But if the car checks out reasonably well, then by all means toss in a new engine and keep driving, Sally.

Dear Tom and Ray:

I have a 1987 Olds Cutlass Ciera in very good condition with 67,000 miles. The brakes stop the car promptly, smoothly and without pulsation. The pads have been replaced once, and the rotors have never been machined. When I took it to a brake and muffler shop, they showed me that one side of my rotors was rusting. To me, it looked like little sand holes. I suggested machining that side, but the mechanic told me both sides would have to be machined, and even that would make the rotors too thin to use. He wouldn't replace the pads unless I replaced the rotors. Can't I just have just one side machined?

--Abe

TOM: That's a good question, Abe, but the answer is no, you really can't machine just one side.

RAY: Theoretically, you could. But in reality, the lathes are set up so that the rotors get pressed by blades from both sides simultaneously. If you apply pressure to only one side, the rotor will "give" whenever there's a bump or defect and you won't really smooth out the surface, which is the whole point of machining. In other words, you'll get a lousy job.

TOM: How does he know? He's done lots of lousy jobs on rotors!

RAY: With your car at 67,000 miles, I suspect your mechanic is right. The rotors probably are worn down to the point where machining them correctly would take them below specification (that is, make them too thin).

TOM: Moreover, if only one side of the rotor is rusted, I'd be concerned that a caliper slide is stuck. Because when a caliper is working properly, the pads should be applying pressure to, and scraping rust off of, both sides simultaneously.

RAY: So this is not the time or place to be a cheapskate, Abe. You really want the calipers working properly and the pads and rotors in perfect, point-to-point contact so you get optimal braking. After all, those doughnut shops can come up on you awfully fast!

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